In software defined networking (SDN) network, after receiving a packet, an SDN switch performs a table lookup in a flow table according to various packet header fields. Flow entries match the packet in priority order. If the matching flow entry is found, counters associated with the matching flow entry are updated and an action in the matching flow entry is applied to the packet, e.g., forward the packet via one or more ports, or drop the packet. If no matching flow entry is found, the packet is forwarded to an SDN controller via a secure channel. The above is a packet lookup and forwarding procedure.
The OpenFlow protocol (OFP) is one exemplary SDN protocol which is currently is utilized. For example, an OpenFlow controller creates a flow entry on an OpenFlow switch according to the OpenFlow protocol. The flow entry includes following content:
Match fields: destination IP=5.6.7.8, action: forward to port 1
After receiving a packet with a destination IP address 5.6.7.8, the OpenFlow switch finds the above flow entry. Then the packet is forwarded to port 1 according to the action in the flow entry.